The purpose of a Doppler ultrasound is to check blood flow. Doctors use the findings to help determine whether there is a blockage, narrowing, or leakage in a blood vessel.

Healthcare professionals use ultrasounds to examine internal structures, such as bones and organs. They use a Doppler ultrasound to analyze how well blood is flowing through the veins and arteries.

This article provides an overview of a Doppler ultrasound, including its uses, what a person can expect, and what the results mean.

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A doctor can use a Doppler ultrasound to check blood flow.

A Doppler ultrasound uses sound waves to create images of how a person's blood is flowing through their veins and arteries. The goal is often to check blood flow through the arms and legs.

During a Doppler ultrasound, a handheld device emits sound waves that bounce off moving objects, such as blood cells. The reflected sound waves create an image of the way the blood is flowing.

There are several types of Doppler ultrasound:

  • A color Doppler helps visualize the movement, speed, and direction of blood flow in color.
  • A power Doppler is a newer form of color Doppler that provides more detail, but it cannot show in which direction blood is flowing.
  • A duplex Doppler takes a standard image of a blood vessel and graphs the data.
  • A spectral Doppler shows blood flow as graphed data, and it can show whether the blood flow is blocked.
  • A continuous-wave Doppler sends a continuous stream of soundwaves, which allows the ultrasound to more accurately measure blood moving at faster speeds.

Healthcare professionals use Doppler ultrasound to learn about a person's blood flow, particularly whether there are any blockages or other irregularities.

The results can help doctors diagnose various conditions, including certain heart conditions.

For example, doctors use Doppler ultrasound to check for:

  • blood vessel damage
  • irregularities in the structure of the heart
  • blockages, such as deep vein thrombosis
  • narrowing or hardening of blood vessels, which can interrupt blood flow to the feet and legs
  • superficial thrombophlebitis, which involves inflammation in a leg vein
  • vascular tumors in the legs
  • thromboangiitis obliterans, a rare disease that causes blood vessels in the hands and feet to swell
  • any changes in heart function, often alongside an electrocardiogram
  • any changes in blood flow following surgery
  • any changes in blood flow during pregnancy or in the fetus

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A person may need a Doppler ultrasound if they have symptoms of a heart condition.

A doctor may order a Doppler ultrasound if a person shows signs of reduced blood flow to the arms, neck, or legs.

The following, for example, can reduce blood flow:

  • blood clots in veins
  • blockages or narrowing of arteries
  • injuries to blood vessels

Typically, a healthcare provider recommends a Doppler ultrasound if a person shows signs or symptoms of certain conditions, such as peripheral arterial disease. This occurs when fatty deposits collect in arteries, restricting blood flow.

Peripheral arterial disease can cause:

  • coldness in the feet or lower parts of the legs
  • weakness or numbness in the legs
  • painful cramping in the leg muscles or hips while walking or climbing stairs
  • changes in the color of the skin
  • shiny skin on the legs

In other cases, a doctor may order a Doppler ultrasound if a person has symptoms of a heart condition, such as:

  • fatigue
  • shortness of breath
  • swelling in the feet, legs, or abdomen

Generally, a doctor tends to order this type of ultrasound when a person:

  • may have damaged blood vessels
  • is currently receiving treatment for a blood flow disorder
  • has recently had a stroke, in which case they will check blood flow in the brain, and the procedure is called a transcranial Doppler

Also, if a fetus is smaller than expected, a Doppler ultrasound can look for any irregularities in blood flow.

A person often does not need to prepare for a Doppler ultrasound.

However, if they smoke, the doctor may ask them to refrain from smoking for a few hours prior to the procedure. Smoking can narrow blood vessels, which can skew the readings.

The Doppler ultrasound is a painless, risk free, and noninvasive procedure. A person may be able to undergo it in their doctor's office, or they may need to visit the radiology unit of a hospital.

Before the ultrasound, a person may need to remove clothing or jewelry on the part of the body being scanned, often the arms or legs. They will then lie on a bed or exam table.

The technician performing the ultrasound may apply blood pressure cuffs around areas such as the calves, ankles, or thighs to measure the pressure in different parts of the arms or legs.

They then apply lubricant to a handheld instrument called a transducer, which they move over the skin to create an image of the blood flow beneath.

The whole procedure typically lasts about 30–45 minutes, and a person can usually leave immediately afterward.

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A doctor will go over the results of a Doppler ultrasound.

The results of a Doppler ultrasound help doctors determine the health of the veins and arteries.

Normal results indicate that the images show no issues such as blockages or narrowing of blood vessels.

If the technician has found an irregularity, it could indicate:

  • a blood clot
  • a blockage in a vein or artery, which may be a buildup of cholesterol, for example
  • narrowing of a blood vessel
  • a coronary artery spasm, which involves an artery in the heart tightening, possibly due to stress

Certain factors can skew the findings of a Doppler ultrasound, such as:

  • obesity
  • an irregular heartbeat
  • cardiovascular disease
  • smoking before the ultrasound

The technician will not discuss the results with the person. They will send the results to the doctor, who will answer any questions. If the technician has discovered an irregularity, the doctor will discuss the next steps.

A Doppler ultrasound helps check for issues that could impede blood flow. It is a noninvasive procedure that requires little, if any, preparation.

A person may undergo a Doppler ultrasound in their doctor's office or the radiology department of a hospital. The technician who performs the ultrasound will send the results to the person's primary care provider, who will discuss the results and any next steps.